Slip clutch

ABSTRACT

A self-propelled forage harvester has a relatively wide mowing implement attached to its forward end and including right and left hand rotary mowing and drawing in drums together with right and left hand rotary conveying drums. A drive transmission for driving these drums includes a pair of identical slip cluthes having respective first sections defined in principal part by a fluid tight cylindrical container having opposite end plates and through the respective centers of which a drive element extends, with the drive element of one clutch being coupled to the drive element of the other clutch by a central drive shaft assembly. The clutches include respective second sections which are in the form of a housing which has a ring-like hub at one end adapted for being coupled to an associated righ-angle transmission unit that is in turn coupled for driving the mowing and drawing in drums at that side. The first and second sections of each clutch are drivingly interconnected by a pair of friction disks mounted for rotation with the second section and respectively biased into friction locked engagement with the opposite end plates forming part of the continer by a spring assembly mounted in an end of the housing remote from the ring-like hub.

This application is a divisional application of application Ser. No.09/695,336, filed 24 Oct. 2000 now U.S. Pat. No. 6,470,658.

The invention concerns an agricultural implement for attachment to atractor or similar self-propelled vehicle, in particular a mowingmachine for the mowing of grass, cereal or other grain crops.

BACKGROUND OF THE INVENTION

In the course of rationalization of the harvesting operation,agricultural implements with large operating widths are applied inconjunction with correspondingly high powered tractors. This appliesparticularly to mowing machines, for the mowing of grass and other graincrops, such as, in particular, corn, that are applied as frontattachment implements for a tractor equipped with a chopper. Therotating tools here consist of intake and mowing drums, with which thecrop is mowed and subsequently conducted to the chopper. In this casethe operating gearbox of the tractor that drives the drive arrangementfor the intake and mowing drums is formed by the central gearbox or themowing height gear box of the chopper. Such forage harvesters employhigh-powered motors up to 500 PS (metric horsepower) wherecorrespondingly high drive power must be applied to the intake andmowing drums that are employed as rotating tools, of which several maybe arranged on both sides of the vertical longitudinal center plane ofthe machine. Since the intake and mowing arrangements operating asrotating tools form large masses that must be accelerated for theinitial acceleration of the mower, the drive arrangement of the tools isequipped with at least one slipping clutch as initial accelerationclutch and simultaneously as a safety clutch by means of which thetorque transmitted between the drive shaft on the part of the vehicleand the drive arrangement of the rotating tools is limited in a mannerknown in itself.

In practical application in operation of such large agriculturalimplements, it has been shown that the maximum torque that can betransmitted by the slipping clutch during initial acceleration of themachine is frequently exceeded, if the initial acceleration on the partof the tractor is performed with a wide open throttle, contrary to theoperating instructions of the manufacturer of the machine, instead ofgradually increasing the application of the accelerator or gas pedal.The slipping clutch then slips under certain circumstances for severalseconds before a friction locking is established through thespring-loaded, ring-shaped friction disks. During the slippage periods,large amounts of heat is generated in the slipping clutches, which areusually configured as dry clutches, that lead to overheating of thefriction surfaces, in particular if the initial acceleration, ifnecessary, must be repeated several times. The forces that can betransmitted by the clutch components are thereby continuously reduced sothat the clutch can become inoperative after only a relatively shortoperating time.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an improved drivefor a large mowing machine of the type described above.

An object of the invention is to provide a drive having improved initialacceleration characteristics which are applicable for use in harvestingoperations in machines of the type indicated above.

A more specific object of the invention is to provide a drive embodyinga slip clutch having a first section in the form of a hub configured asa ring-shaped container filled with fluid, with ring-shaped frictiondisks being engaged with end plates forming part of the container andmounted on a second clutch section for rotation with the second sectionwhich defines a housing surrounding the container, the fluid acting toabsorb heat so that over-heating of the friction disks due to improperperformance of the starting or initial acceleration process of theimplement is largely avoided. The cooling fluid, such as water,contained in the ring-shaped container not only absorbs the heatgenerated by the clutching process, but conducts it to the surroundingsover heat exchange surfaces provided by the ring-shaped container. Inthis way a considerable increase in the durability of the slip clutch isattained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a machine for mowing corn and similarstalk-like crop in connection with a chopper.

FIG. 2 is an enlarged, partial section of a plan view of the region ofthe drive arrangement of the mowing machine of FIG. 1.

FIG. 3 is an enlarged, axial sectional view through a detail of thedrive arrangement according to FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Preliminarily, it is to be noted that the terms “left” and “right” areto be considered relative to an observer standing behind, and facing inthe direction of forward travel of, the machine illustrated in FIG. 1.

Referring now to FIG. 1, there is shown an agricultural implement in theform of a mowing implement or machine 1 attached to a tractor or similarself-propelled vehicle, here shown as a self-propelled forage harvester2, for the mowing of corn and similar stalk-like crops. The forageharvester 2 includes a chopper 3 that is arranged centrally with respectto the mowing implement 1. The cut crop is conducted over intake rollsto a chopper blower, not shown in any further detail, in which it ischopped into short lengths and then conveyed over an exhaust duct 4 to amobile container such as an agricultural self-loading forage box, forexample.

The mowing machine 1, is moved forward by the vehicle 2 in the directionof operation or driving according to the arrow F, and, in the embodimentshown, includes a total of ten rotating tools in the form of intake andmowing drums 5 through 14, respectively, with the drums 5 through 9being arranged at the left side of a vertical, longitudinal center plane15 of the machine, and the drums 10 through 14 being arranged at theright side of the center plane 15. The two groups of intake and mowingdrums 5 through 9, on the one hand, and 10 through 14, on the otherhand, are arranged in a mirror image symmetrically about thelongitudinal center plane 15. In addition, further conveyor drums 16, 17and 18 are located behind the neighboring intake and mowing drums 6through 9 for further conveying of the crop cut by these drums and thedrum 5 as well, while further conveyor drums 19, 20 and 21 are locatedbehind the neighboring intake and mowing 10 through 13, for furtherhandling of the crop cut by these drums and the drum 14 as well.

For driving the rotary tools in the form of the intake and mowing drums5 through 14 as well as the conveying drums 16 through 21, the mowingmachine 1 is equipped with a drive arrangement, designated in itsentirety by the numeral 22, coupled to a gearbox 23 on the part of thevehicle that, in the embodiment shown, is formed by the central ormowing height gearbox of the chopper 3. From the operating gearbox 23,the drive is transmitted over an articulated shaft 24 to a gearbox 25and from this over an articulated shaft 26 to the drive arrangement 22.

In the embodiment shown, the drive arrangement 22 includes a clutcharrangement acting as a safety device while transferring torque duringinitial acceleration, the clutch arrangement being in the form of twoclutches 27 and 28 that are rigidly connected with each other over aconnecting shaft 29 with sleeve couplings 30. The two clutches 27 and 28are configured identically and are arranged as mirror imagessymmetrically to each other on opposite sides of the verticallongitudinal center plane 15. The clutches 27 and 28 are respectivelyconnected with angled gear boxes 31 and 32 that transmit the drive takenfrom the tractor 2 to respective shaft drive-lines (not shown) supportedin bearings, free to rotate, in a frame tube 33 for the drive of theleft half of the machine with the intake and mowing drums 5 through 9,or the right half of the machine with the intake and mowing drums 10through 14. For its part, the frame tube 33 is fastened to a base frameof the mowing machine 1 in a manner not shown in any further detail.Furthermore, as can be seen in FIG. 2, a shaft section 34 of thearticulated shaft 26 continues through the gear box 31 and extends at 34a into the clutch 27 in which it is retained by a multi-edge connection35 with an axial play for movement.

Since the two clutches 27 and 28 are identical in design, theirconfiguration shall be explained in greater detail below only on thebasis of the clutch 27 together with the enlarged view in FIG. 3.Accordingly, the clutch 27 includes a first clutch section defining afirst clutch hub configured as a container 38 enclosed on all sides thatincludes a cylindrical inner sleeve 39 providing a hub opening 36 thataccepts the stub shaft 34 a of the drive shaft section 34 on the part ofthe vehicle introduced into the clutch 27. The container 38 alsoincludes an outer sleeve or cylindrical wall 40 that is joined toopposite, parallel end plates 43 and 44 so as to define an annular,space 41, that is filled with cooling fluid, such as water, and isclosed on all sides except for a fill opening provided in the outersleeve 40, which opening is closed after completion of the fillingprocess by a threaded plug 42 and a sealing ring so that the space 41 isfluid tight. The cylindrical sleeve 39 extends through the center of,and is fixed to, the end plate 43 and has an end which terminates withinthe container 38.

The clutch 27 further includes a second clutch section in the form of aclutch housing 37 including an end plate or hub 58 having an opening 59provided with internal splines or a multi-wedge connection 60 throughwhich the drive connection to the angled gearbox 31 is made for drivingthe rotary tools on that side of the vehicle.

Respectively located on the outside of the end plates 43 and 44 of thecontainer 38 are ring-shaped or annular friction disks 45 and 46 thatare respectively rigidly connected with ring-shaped or annular driverdisks or backing plates 47 and 48. The rigid connection of thering-shaped friction disks 45 and 46 with the ring-shaped driver disks47 and 48 can be performed by mechanical connecting links, by bonding,by spraying with friction disk material or any other appropriate manner.The clutch housing 37 is configured so as to define a cylindricalenclosure or sleeve 50 that encompasses the container 38 and includes ahousing portion extending axially beyond the end plate 44. Guide socketsor tabs 49 form part of and are angled at right angles from theremaining portions of the driver disks or backing plates 47 and 48 andare retained in circumferential guide slots provided in the cylindricalenclosure or sleeve 50 so as to extend parallel to the axis of rotationand to provide axial play for the disks 47 and 48 and also for couplingthe friction disks 47 and 48 for rotation with the cylindrical enclosure50. Otherwise, the cylindrical enclosure 50 is configured as a gratingwith openings 51, that improve the dissipation of heat from thering-shaped container 38.

The friction disks 45 and 46 are spring loaded for effecting a driveconnection that is a function of the torque between the ring-shapedcontainer 38 forming the clutch hub and the clutch housing 37. Thisspring loading is provided by a ring-shaped spring package or assembly52, mounted within and to the portion of the clutch housing 37 thatextends axially beyond the end plate 44, the spring package 52consisting of a ring of individual helical compression springs 53 whoseline of force is parallel to a rotational axis R of the clutch. The ringof springs 53 are supported at their opposite end faces respectively byretaining rings 54 and 55, with the ring 54 bearing against the driverdisk or backing plate 48 to which the friction disk 45 is fixed.

The compression of the compression springs 53 and thereby the maximumtorque controlled by the contact pressure of the friction disks 45 and46 at which the clutch 27 slips is adjusted by an adjustment ring 56that is provided with detent cams 57 for a locking engagement inaperture openings of the clutch housing 37. Here, two or several ringsand aperture openings are preferably provided that are spaced from oneanother in the direction of the clutch axis R, that are spaced for theirpart in the circumferential direction corresponding to the detent cams57 of the adjustment ring 56. In the installed condition, the adjustmentring 56 is positioned with its inner end in contact with an outer faceof the retaining ring 55, and thereby determines in the installedcondition the pressure force, depending on which aperture openingengages a locking cam 57. As long as an adjustment of the torque throughthe package of compression springs 52 can be omitted, obviously a singlering of aperture openings in the clutch housing 37 would be sufficientfor the locking of the adjustment ring 56.

The end plate or hub 58 of the housing 37 is located on the opposite endof the housing from the adjustment ring 56 and, together with the endplate 43 of the container 38, sandwiches the backing plate 47 with thefriction disk 45. With the container 38 being mounted for shiftingaxially relative to the housing 37, the force exerted by the compressionsprings 52 acts to establish the predetermined force of frictionalengagement between the friction disk 45 and the container end plate 43.

At its end opposite the introduction opening for the stub drive shaft 34a, the inner sleeve 39 is rigidly connected, for example welded to acoaxial stub shaft 61. Furthermore, the stub shaft 61 is rigidlyconnected or welded to the end plate 44 of the ring-shaped container 38.The same goes for the end plate 43 with respect to the inner sleeve 39.The stub shaft 61 extends through the spring package 52 to theconnecting shaft 29, with which it is connected over the sleeve coupling30. The connection with sleeve coupling 30 is again performed by amulti-wedge or spline connection.

Furthermore, an arrangement of the grooves and ribs 62 can be seen inFIG. 3 that is limited to the central region of the sleeve bore 36 whichis configured for the multi-wedge connection 35 (FIG. 2) with thecorrespondingly configured stub shaft 34 a of the shaft section 34.

When the arrangement is coupled, the power flows over the spring loadedfriction disks 45 and 46 from the ring-shaped container 38, set intorotation by the drive shaft section 34, to the clutch housing 37, inparticular, the end plate or hub 58 whose rotational movement istransmitted in turn through the multi-wedge connection 60 to the gearbox31. Here the rotational drive is transmitted simultaneously over thestub shaft 61 to the connecting shaft 29 and from there over the stubshaft 61′, that corresponds to the stub shaft 61, to the ring-shapedcontainer 38′ and the clutch housing 37′ of the clutch 28 over themulti-wedge connection 60′ to the angled gearbox 32.

If during the operation of the clutch 27, the pre-determined torque isexceeded, then the clutch will slip, and a relative rotational movementwill occur between the clutch housing 37 and the ring-shaped container38 with sliding friction occurring at the respective interfaces betweenthe ring-shaped disks 45 and 46 and the end plates 43 and 44 of thering-shaped container 38. The relative rotational movement is madepossible by the clutch housing 37 with its cylindrical sleeve orenclosure 50 that concentrically surrounds and is spaced from thering-shaped container 38 so as to leave a circumferential ring shapedvoid 63. It will be appreciated that heat generated at the interface ofthe clutch friction disks 45 and 46 and the container end plates 43 and44 will be dissipated by the liquid coolant carried inside the container38. Further, the various slots or openings 51 in the enclosure 50 alsohelp in the dissipation of heat generated when the clutch 27 slips.

What is claimed is:
 1. A slip clutch for use in an agriculturalimplement, comprising: a) first and second clutch sections having arotational axis; b) said first clutch section defining a fluid-tightcontainer having opposite ends respectively defined by a first andsecond end plates disposed perpendicular to said axis and said secondclutch section being located exteriorly of said fluid tight-container;c) a first and second friction disks being respectively mounted to saidsecond clutch section for rotation therewith and for axial movementtoward and away from said first and second end plates; and d) a biasingarrangement urging said first and second friction disks respectivelyinto locked friction engagement with said first and second end plateswith a predetermined engaging force, whereby, upon said slip clutchexperiencing an overload, said first and second friction disks willrespectively slip relative to said first and second end plates thusgenerating heat which is dissipated by liquid coolant contained in saidfluid-tight container.
 2. The slip clutch as defined in claim 1 whereinsaid second clutch section includes: a) a housing surrounding saidfluid-tight container and having a housing portion extending axiallybeyond said second end plate; b) an annular spring retainer forming partof said biasing arrangement and being mounted within said housingportion of said housing; and c) a plurality of coil compression springsbeing mounted between said spring retainer and said first friction disk.3. The slip clutch as defined in claim 1 wherein said second clutchsection includes: a) a cylindrical housing spaced radially outward fromsaid first clutch section and provided with a plurality of axiallyextending openings; b) an annular backing plate including a plurality ofaxially extending tabs respectively located in said plurality of axiallyextending openings; and c) said first friction disk being fixed to saidannular backing plate, whereby said first friction disk is mounted foraxial movement toward and away from said first end plate while beingcoupled for rotation with said second clutch section.
 4. The slip clutchas defined in claim 1 wherein: a) said fluid-tight container isgenerally cylindrical; b) a cylindrical sleeve forms part of saidcontainer, extends through said first end plate and has opposite firstand second ends respectively terminating inside said container andadjacent said first end plate; c) a stub shaft extends through saidsecond end plate and is fixed to said first end of said sleeve and tosaid second end plate; d) said second clutch section includes a hubdisposed in concentric relationship to said second end of the sleeve ata location outside said fluid-tight container; e) said stub shaftincludes a section located outside said fluid-tight container andprovided with connection splines about its exterior; f) said sleeve isprovided with internal connection splines; and g) said hub is providedwith connection splines on its interior, whereby said cylindrical sleeveis adapted for being connected to a power input shaft, said hubestablishes an output adapted for being connected to a driven elementand said stub shaft is adapted for transferring input power beyond saidslip clutch.
 5. The slip clutch as defined in claim 1 wherein: a) saidfluid-tight container is generally cylindrical; b) said second clutchsection includes a housing having a cylindrical wall disposed inconcentric relationship to, and spaced from, said container so as todefine an annular void between the container and the housing; and c)said cylindrical wall is provided with a plurality of openings fordissipating heat generated by relative movement between said firstfriction disk and said first end plate when the clutch is overloaded andslips.